Liquid crystal display device and method for fabricating the same

ABSTRACT

A method for fabricating a liquid crystal display device, which includes a liquid crystal layer, a pair of electrodes for use to apply a voltage to the liquid crystal layer, and at least one inorganic alignment film. The inorganic alignment film makes direct contact with the liquid crystal layer and is made of a crystalline conductive film where crystal grains are oriented in a predetermined direction preferentially.

This application is a Divisional of co-pending application Ser. No.10/621,522, filed on Jul. 18, 2003, and for which priority is claimedunder 35 U.S.C. § 120; and this application claims priority ofapplication No. 2002-209129 filed in Japan on Jul. 18, 2002 under 35U.S.C. § 119; the entire contents of all are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and amethod for fabricating the device. As used herein, the “liquid crystaldisplay devices” include both a direct viewing liquid crystal displaydevice and a projection type liquid crystal display device.

2. Description of the Related Art

A liquid crystal display (LCD) conducts a display operation by utilizingvariations in the polarization states of an incoming light ray beingtransmitted through the liquid crystal layer thereof. The polarizationstate of the incoming light ray is changed by orientation directions ofliquid crystal molecules, which in turn are changeable with theapplication of a voltage to the liquid crystal layer. In the LCD, adisplay panel, including the liquid crystal layer and electrodes andcircuit components for use to apply a voltage to the liquid crystallayer, will be referred to herein as an “LCD panel”. The LCD includesnot only the LCD panel but also a driver circuit, a power supply circuitand a light source. Portions of the driver circuit and power supplycircuit may either form integral parts of the LCD panel or be mounted onthe LCD panel.

The LCD panel typically includes two substrates and a liquid crystallayer provided between the substrates. Each of the two substratesincludes an alignment film that faces the liquid crystal layer. Thealignment films are provided so as to align liquid crystal molecules ina predetermined direction in the liquid crystal layer.

The alignment films are normally formed in the following manner.

Specifically, first, an organic polymer film of polyimide, for example,is deposited over a substrate on which electrodes for use to apply avoltage to the liquid crystal layer and circuit components (such asswitching elements and lines) for supplying a predetermined voltage tothe electrodes are provided. Next, the surface of this organic polymerfilm is mechanically rubbed directly with a cloth in a predetermineddirection (subjected to a rubbing treatment), thereby obtaining analignment film having the function of aligning the liquid crystalmolecules in the predetermined direction.

It is believed that the alignment film should define the orientationdirection of the liquid crystal molecules due to the shape effects offine grooves that have been formed on the surface of the film as aresult of the rubbing treatment, the stretching effects of organicpolymers that make up the film, and the anisotropic electrostaticeffects induced on the surface of the film.

However, if the liquid crystal molecules are aligned by the conventionalrubbing treatment, then fibers of the cloth and impurities such asdebris and dust may be deposited on the surface of the film or on thesubstrate, thus possibly causing some defects or deterioration on thedisplay and decreasing the yield or reliability. Also, the staticelectricity, produced during the rubbing treatment, may cause adielectric breakdown in thin-film transistors (TFTs) ormetal-insulator-metal (MIM) elements, thus also bringing about somedefects in the display. Furthermore, in the rubbing treatment, thepressure cannot always be applied sufficiently uniformly but may beapplied locally non-uniformly. As a result, the liquid crystal moleculesmay have their pretilt angles disturbed to form some rubbing stripes invery small domains of the liquid crystal layer. In that case, thedisplay quality may be seriously affected.

Furthermore, the rubbing treatment is preferably carried out in anenvironment that is as free from static electricity or dust as possible.Thus, in the actual production line, the rubbing treatment needs to beperformed separately from the place where the process step of formingthe organic polymer film is being carried out. In addition, after therubbing treatment process has been carried out, the substrate needs tobe subjected to a wet cleaning process step, which requires a hugequantity of cleaning liquid. Consequently, the conventional rubbingtreatment significantly increases the number of required process stepsand the cost of the LCD panel manufacturing process.

Thus, to overcome these problems, various non-contact alignmenttreatment techniques have been proposed. A method of forming analignment film by exposing an organic polymer film, includingphotosensitive molecules, to a polarized ultraviolet ray is disclosed inJapanese Patent No. 2608661 and Japanese Laid-Open Publication No.9-197406, for example.

Also, a so-called “optical alignment technique” of controlling thepretilt angle to be defined by a polyimide film for liquid crystalmolecules by obliquely irradiating the polyimide film with a(non-polarized or polarized) ultraviolet ray is disclosed in Mol. Cryst.Liq. Cryst. Sci. Technol., Sect. A, 333, 165 (1999).

Furthermore, techniques of forming an alignment film by irradiating analignment film with another energy beam such as an electron beam, an ionbeam or a laser beam onto the surface of a target film unlike theoptical alignment technique described above are disclosed in JapaneseLaid-Open Publications No. 2-222927, No. 6-130391, No. 7-56172, and No.9-218409, for example.

In any of these alternative techniques, when exposed to the energy beam,the surface of the alignment film is physically etched anisotropically,thereby forming a great number of fine grooves. Thus, the liquid crystalmolecules are believed to be aligned anisotropically along thosegrooves. According to these energy beam methods, however, some damage isalso done on the material of the film being exposed to the energy beam.Accordingly, alignment defects may be formed or the reliability maydecrease. For that reason, it is difficult to optimize the energy beamirradiation conditions.

Japanese Laid-Open Publication No. 11-271773 discloses a method ofarranging the atomic structures of an alignment film in a desireddirection by exposing a film, which has been formed on a substrate by adry patterning process (e.g., an evaporation process, a sputteringprocess, an ion beam deposition process, a CVD process or a PECVDprocess), to a particle beam. In this method, the material of thealignment film must be optically transparent and amorphous or fineparticular. Examples of specific alignment film materials disclosedtherein include glass, graphite, diamond, SiC, SiO₂, Si₃N₄, Al₂O₃, SnO₂,InTiO₂, InZnO₂ and ZnTiO₂. On the other hand, Japanese Laid-OpenPublication No. 11-271774 discloses a technique of aligning liquidcrystal molecules in which a film, producing bonds to be aligned on thesurface preferentially, is formed and the surface thereof is exposed to(the impact of) a particle beam consisting of atoms, molecules, ions orclusters, thereby producing bonds that are aligned in a directionpreferentially and anisotropically. Examples of specific alignment filmmaterials disclosed therein include graphite, diamond, SiC, SiO₂, Si₃N₄,Al₂O₃, SnO₂, InTiO₂, InZnO₂ and ZnTiO₂.

In the techniques disclosed in Japanese Laid-Open Publications No.11-271773 and No. 11-271774, however, a film having a basicallyisotropic structure is exposed to a particle beam, thereby producing apreferential alignment for the atomic arrangements or bonds and aligningthe liquid crystal molecules by utilizing the anisotropy. Thus,according to these techniques, the anchoring force is relatively weakand good reliability may not be achieved. Also, although JapaneseLaid-Open Publication No. 11-271774 describes that a crystalline orpolycrystalline material may contribute to forming the alignment filmeither indirectly or directly, the publication provides no specificdisclosure about that.

Furthermore, Japanese Laid-Open Publications No. 2-294618 and No.2001-21891 disclose a technique of adding an alignment film function toconductive films that are used to apply a voltage to a liquid crystallayer. Specifically, Japanese Laid-Open Publication No. 2-294618discloses that transparent conductive films of ITO, which sandwich theliquid crystal layer, may have anchoring force when formed by an obliqueevaporation process. On the other hand, Japanese Laid-Open PublicationNo. 2001-21891 discloses a method of providing anisotropy for conductivefilms by exposing the surface of electrodes made of an inorganicmaterial such as ITO, Al or an Al alloy to an energy beam directly andthereby etching the surface of the electrodes anisotropically.

However, the conventional conductive film is normally an amorphous filmor a polycrystalline film with random crystallographic orientations.Thus, it is difficult to maintain sufficient anchoring force,contributing to aligning the orientation directions of liquid crystalmolecules constantly, with good reproducibility just by carrying out theoblique evaporation process as disclosed in Japanese Laid-OpenPublication No. 2-294618 or by patterning the surface of the conductivefilms into an anisotropic shape (e.g., steps or grooves) by ananisotropic etching process as disclosed in Japanese Laid-OpenPublication No. 2001-21891. In an active-matrix-addressed liquid crystaldisplay device, in particular, the orientation directions of liquidcrystal molecules are often disturbed near steps that are created by thecomplicated stacking structure. Accordingly, to make a commerciallyviable product, the anchoring force thereof must be increased.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a highly reliable liquid crystaldisplay device, which can be fabricated by a simplified manufacturingprocess that needs no rubbing treatment to make an alignment film, and amethod for fabricating such a liquid crystal display device.

A liquid crystal display device according to a preferred embodiment ofthe present invention preferably includes: a liquid crystal layer; apair of electrodes for use to apply a voltage to the liquid crystallayer; and at least one inorganic alignment film. The inorganicalignment film preferably makes direct contact with the liquid crystallayer and is preferably made of a crystalline conductive film wherecrystal grains are oriented in a predetermined direction preferentially.

In one preferred embodiment of the present invention, the at least oneinorganic alignment film preferably functions as at least a portion ofthe pair of electrodes.

In another preferred embodiment, the crystalline conductive filmpreferably has a groove, which extends in a direction associated withthe predetermined direction and which faces the liquid crystal layer.

In still another preferred embodiment, the crystalline conductive filmis preferably made of indium tin oxide, Al or an Al alloy.

In yet another preferred embodiment, the crystalline conductive filmpreferably has a degree of crystallinity of at least about 60%.

In yet another preferred embodiment, the crystal grains preferably havea cubic crystalline structure, and the predetermined direction may be<111> directions of the crystal grains.

In this particular preferred embodiment, the crystalline conductive filmpreferably has a diffraction intensity ratio of about 0.25 or less in anX-ray diffraction pattern. The diffraction intensity ratio is preferablydefined by I(400)/I(222)≡Ip, where I(400) represents a peak intensity ofa (400) plane and I(222) represents a peak intensity of a (222) plane.

In an alternative preferred embodiment, the crystal grains preferablyhave a cubic crystalline structure, and the predetermined direction maybe <110> directions of the crystal grains.

In yet another preferred embodiment, the crystalline conductive film ispreferably made of indium tin oxide and preferably exhibits atransmittance of about 70% or more with respect to a light ray having awavelength of about 400 nm and a transmittance of about 80% or more withrespect to a light ray having a wavelength of about 550 nm when thethickness of the crystalline conductive film is 120 nm.

In yet another preferred embodiment, the device preferably furtherincludes: an illumination optical system for illuminating the liquidcrystal layer with light; and a projection optical system for projectingthe light that has been transmitted through the liquid crystal layer.

A method for fabricating a liquid crystal display device according to apreferred embodiment of the present invention is preferably designed tomake a liquid crystal display device including: a liquid crystal layer;a pair of electrodes for use to apply a voltage to the liquid crystallayer; and at least one inorganic alignment film, which makes directcontact with the liquid crystal layer and which is made of a crystallineconductive film. The method preferably includes the steps of: formingthe crystalline conductive film, in which crystal grains are oriented ina predetermined direction preferentially, on a substrate; and formingthe liquid crystal layer on the crystalline conductive film.

In one preferred embodiment of the present invention, the methodpreferably further includes the step of irradiating the crystallineconductive film with an energy beam at an angle that is associated withthe predetermined direction.

In this particular preferred embodiment, the step of forming thecrystalline conductive film preferably includes the step of forming thecrystalline conductive film in which the crystal grains have a cubiccrystalline structure and are oriented in <111> directions thereof. Thestep of irradiating the crystalline conductive film with the energy beampreferably includes the step of irradiating the crystalline conductivefilm such that the energy beam defines an angle of incidence of about 30degrees to about 50 degrees with respect to a normal to the surface ofthe substrate.

In an alternative preferred embodiment, the step of forming thecrystalline conductive film preferably includes the step of forming thecrystalline conductive film in which the crystal grains have a cubiccrystalline structure and are oriented in <110> directions thereof. Thestep of irradiating the crystalline conductive film with the energy beampreferably includes the step of irradiating the crystalline conductivefilm such that the energy beam defines an angle of incidence of about 35degrees to about 55 degrees with respect to a normal to the surface ofthe substrate.

In yet another preferred embodiment, the step of irradiating thecrystalline conductive film with the energy beam preferably includes thestep of irradiating the crystalline conductive film with at least oneenergy beam that is selected from the group consisting of an excimerlaser beam, an ultraviolet ray, an electron beam and a particle beam.

Other features, elements, processes, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating thestructure of a liquid crystal display device 100 according to apreferred embodiment of the present invention.

FIG. 2 schematically illustrates the crystal structure of indium oxide.

FIG. 3 schematically shows the crystallographic planes of a cubiccrystal unit cell (or crystal lattice).

FIG. 4 shows the XRD pattern of a crystalline ITO film for use in aliquid crystal display device according to a preferred embodiment of thepresent invention and the crystallographic planes represented by therespective peaks of diffraction.

FIG. 5 schematically illustrates a configuration for an ion beam emitter10 which is preferably used to carry out an alignment treatment on acrystalline conductive film in a preferred embodiment of the presentinvention.

FIG. 6 schematically illustrates an exemplary arrangement for aprojection type liquid crystal display device 200 according to aspecific preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, the structures and functions of a liquid crystal displaydevice according to preferred embodiments of the present invention willbe described with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view illustrating a structure fora liquid crystal display device 100 according to a preferred embodimentof the present invention. As shown in FIG. 1, the liquid crystal displaydevice 100 preferably includes a liquid crystal layer 5, and a pair ofelectrodes 2 and 6 for use to apply a voltage to the liquid crystallayer 5. Each of these electrodes 2 and 6 may also function as aninorganic alignment film made of a crystalline conductive film wherecrystal grains are oriented in a predetermined direction preferentially.The liquid crystal layer 5 is provided in the gap created between a pairof substrates 1 and 7 by spacers 3, and is sealed with a seal member 4.The electrodes 2 and 6 are provided on the substrates 1 and 7,respectively, so as to face the liquid crystal layer 5, and are used toapply a voltage that regulates the optical orientation states of theliquid crystal layer 5. In an active-matrix-addressed liquid crystaldisplay device, the electrodes 2 and 6 may be a pixel electrode and acounter electrode, respectively. In that case, each pixel will includeboth of these electrodes 2 and 6.

The liquid crystal display device 100 shown in FIG. 1 uses inorganicalignment films, made of crystalline conductive films, as the electrodes2 and 6. However, depending on the orientation mode of the liquidcrystal layer 5, the inorganic alignment film may be provided on justone of the two substrates 1 and 7 so as to face the liquid crystal layer5. As another alternative, the inorganic alignment films may be providedseparately from the electrodes 2 and 6. As used herein, the “inorganicalignment film” may be any of various non-organic alignment films andmay be made of a metal, a metal oxide or a metal nitride, for example.

The liquid crystal display device 100 of this preferred embodimentincludes inorganic alignment films (also functioning as the electrodes 2and 6 in FIG. 1) made of crystalline conductive films in which crystalgrains are oriented in a predetermined direction preferentially.Accordingly, those crystalline conductive films, including the alignedcrystal grains, may be formed by any of various methods, and do not haveto be subjected to any rubbing treatment unlike the conventional organicpolymer alignment film. These inorganic alignment films have electricalconductivity and can be used as the electrodes 2 and 6 as alreadydescribed above. It should be noted, however, that if the electrodes foruse to apply a voltage to the liquid crystal layer cannot be used asalignment films (e.g., in IPS mode), then inorganic alignment films maybe provided independent of the electrodes. Even so, those additionalinorganic alignment films can also be formed by the process step offorming the electrodes or lines that are connected to the electrodes.Thus, the manufacturing process of the liquid crystal display device canalso be simplified. As a result, the manufacturing cost of the liquidcrystal display device can be reduced and the yield thereof can beincreased.

In the liquid crystal layer 5, the liquid crystal molecules (not shown)are aligned in a direction that is associated with the preferentialorientation direction of the crystal grains in the crystallineconductive films. In addition, the crystalline conductive films canimpose stronger anchoring force than the alignment films described inJapanese Laid-Open Publication Nos. 11-271773 and 11-271774, and canmaintain a stabilized orientation state in the liquid crystal layer 5.

Also, the surface of the crystalline conductive films is preferablyprovided with physical anisotropy by irradiating the crystallineconductive films with an energy beam from the direction that isassociated with the preferential orientation direction of the crystalgrains in the crystalline conductive films. Then, the crystallineconductive films can exhibit even stronger anchoring force, thus furtherincreasing the uniformity and stability of the orientation state of theliquid crystal layer. Furthermore, the crystalline conductive films aremade of an inorganic material, and are much less damaged than theconventional organic alignment films even when exposed to an energybeam. Accordingly, there is no need to worry about the unwanted decreasein reliability, which is often the case with the conventional organicalignment films. Examples of preferred energy beams include particlebeams (consisting of atoms, molecules, ions or clusters) as disclosed inJapanese Laid-Open Publications Nos. 11-271773 and 11-271774 and variousother energy beams (including an excimer laser beam, an ultraviolet rayand an electron beam) as disclosed in Japanese Laid-Open Publication No.2001-21891.

As used herein, the “direction that is associated with the preferentialorientation direction of crystal grains” is a direction that satisfies apredetermined relationship with the preferential orientation directionof the crystal grains. The “predetermined relationship”, in turn,depends on the crystallographic system (or crystal structure) of thecrystal grains. The orientation direction of the liquid crystalmolecules, which is controlled by the inorganic alignment films (i.e.,the crystalline conductive films), is not always identical to (orparallel to) the preferential orientation direction of the crystalgrains. However, the orientation direction of the liquid crystalmolecules is determined according to the crystallographic system of thecrystal grains and is associated with the preferential orientationdirection of the crystal grains. Also, by radiating the energy beam froma direction that satisfies a certain relationship with the preferentialorientation direction of the crystal grains, the anchoring force can beincreased in the direction that is associated with the preferentialorientation direction of the crystal grains. Thus, the energy beamirradiating direction is also determined according to thecrystallographic system of the crystal grains.

When the crystalline conductive films are exposed to an energy beam, theanchoring force thereof is believed to be increased by the following twomechanisms (1) and (2) in combination. The degrees of contribution ofthese two mechanisms are changeable with the type of the energy beam andthe material of the crystalline conductive films.

-   -   (1) When exposed to an energy beam from a certain direction, the        crystalline conductive films are etched anisotropically to        define a groove structure, which extends in a predetermined        direction that is associated with the preferential orientation        direction thereof. Due to a grating effect (shape effect) caused        by this groove structure, the orientation directions of the        liquid crystal molecules are controlled.    -   (2) With the energy beam incident from a certain direction on        the crystalline conductive films, bonds in a particular        direction (e.g., a direction that is perpendicular to, or        intersects with, the orientation direction of the crystal        grains) may be either selectively cut off or newly produced,        thus increasing the anisotropy of bonds existing around the        surface of the crystalline conductive films and increasing the        anchoring force.

In the liquid crystal display device 100 of this preferred embodiment,the electrodes 2 and 6 for use to apply a voltage to the liquid crystallayer 5 also function as inorganic alignment films. Compared to thearrangement in which electrically insulating, organic alignment filmsare provided on the electrodes 2 and 6 so as to face the liquid crystallayer 5, the arrangement shown in FIG. 1 can achieve the followingadvantages (1) through (3):

-   -   (1) The transmittance of the display panel does not decrease due        to the absorption of light into the alignment films.    -   (2) An image persistence (image sticking) phenomenon, caused by        polarized charges remaining in the interfaces between the        electrically insulating alignment films and the liquid crystal        layer, and other unwanted phenomena can be avoided.    -   (3) The display quality is not affected by the thermally or        optically induced deterioration of the organic alignment films.

Hereinafter, the structure of the crystalline conductive films to beused as the inorganic alignment films in the liquid crystal displaydevice according to this preferred embodiment of the present inventionand a method for forming the crystalline conductive films will bedescribed in further detail.

How to Form Crystalline Conductive Films

In a liquid crystal display device, a film of indium tin oxide (ITO) isnormally used as a material for the transparent electrodes thereof. TheITO film is an aggregate of ITO particles and may or may not exhibitcrystallinity, which is controllable by adjusting the conditions todeposit the film, for example. According to a report, indium oxide(In₂O₃) has two crystallographic systems of cubic In₂O₃[I] and hexagonalIn₂O₃[II]. In a low-temperature film synthesis process to be carried outat a normal or lower pressure, the cubic In₂O₃[I], which is called“bixbyite” belonging to a space group I_(a3)) as schematically shown inFIG. 2, is prevailing. The crystalline conductive films for use in theliquid crystal display device according to this preferred embodiment arepreferably made of ITO films having the cubic crystal structure.

An ITO film in which crystal grains are oriented in a particulardirection preferentially may be formed by a high-density plasma-assistedEB evaporation (HDPE) process, which is a low-temperature depositionprocess by an activating evaporation technique as described in OyoButuri, Vol. 64, No. 12, pp. 1225-1229 (1995). Examples of otherpreferred processes include physical deposition processes such as vacuumevaporation, ion plating and sputtering processes and a chemical vapordeposition (CVD) process. In particular, when the HDPE process isadopted, a crystalline ITO film with a relatively low resistivity (e.g.,about 2×10⁻⁴ Ω·cm or less) can be formed at a relatively low temperature(e.g., at a substrate temperature of about 150° C. to about 200° C.).

The crystal structure and the degree of crystallinity of the ITO filmcan be identified and estimated by analyzing the X-ray diffraction (XRD)pattern thereof (e.g., by locating crystal peaks resulting from theindium oxide component). When a crystalline ITO film is subjected to athin film XRD analysis, peaks representing (222), (400), (211), (440)and (622) planes that mainly result from indium oxide are detected. FIG.3 schematically shows the crystallographic planes of a cubic crystalunit cell (or crystal lattice). FIG. 4 shows the XRD pattern of apreferred crystalline ITO film and crystallographic planes representedby the respective peaks of diffraction.

As for the orientation directions of the crystal grains in thecrystalline ITO film, the preferential orientation direction may bedetermined by the ratio of the peak intensity of the (400) plane to thatof the (222) plane among the diffraction peaks shown in FIG. 4. Morespecifically, the preferential orientation direction may be estimatedquantitatively by the following XRD peak intensity ratio:I(400)/I(222)≡Ipwhere I(400) represents the peak intensity of the (400) plane and I(222)represents the peak intensity of the (222) plane. If the Ip value isless than about 0.33, then <111> orientation directions may be regardedas the preferential orientation direction. On the other hand, if the Ipvalue is equal to or greater than about 0.33, then <100> orientationdirections may be regarded as the preferential orientation directions.In the same way, it is also possible to determine, by the ratio of thepeak intensity of the (440) plane to that of the (400) plane, whetherthe <110> orientation directions are preferential or not. It should benoted that according to crystal diffraction data values (i.e., ASTMvalues), the peak intensity ratio Ip is about 100.33 when crystal grainsof indium oxide are randomly oriented.

The crystalline ITO films for use in the liquid crystal display deviceof this preferred embodiment preferably have an Ip value of less thanabout 0.33 (i.e., either the <111> orientation directions or the <110>orientation directions are preferably preferential) and more preferablyhave an Ip value of about 0.25 or less. The reason is as follows.Specifically, in an ITO film with an Ip value of about 0.25 or less, the<111> orientation is even more dominating, and therefore, theorientation directions are much less disturbed on the grain boundary andsub-grains are oriented in substantially the same direction in thecrystal grains. Thus, such an ITO film can impose orientation control onthe liquid crystal molecules more uniformly. The crystal grainstypically have an average grain size of about 250 nm or more. In thatcase, each of those crystal grains preferably consists of sub-grainswith an average grain size of about 20 nm to about 70 nm.

Furthermore, the crystalline conductive films preferably have a degreeof crystallinity of at least about 60%, more preferably about 90% ormore. The “degree of crystallinity” is herein estimated by the peakintensities of an XRD pattern. More specifically, the degree ofcrystallinity is calculated as the percentage of the sum of XRD peakintensities resulting from crystalline portions to the integral of thepeak intensities resulting from not only the crystalline portions butalso non-crystalline portions. If a crystalline conductive film has adegree of crystallinity of less than about 60%, then the crystallineconductive film cannot impose sufficient orientation control on liquidcrystal molecules and may be unable to function as an alignment filmappropriately.

It is known that the electrical properties of an ITO film are closelycorrelated with various factors including impurities, crystallographicdefects such as oxygen defects and lattice defects, and grainboundaries. Generally speaking, a crystalline ITO film tends to have alower resistivity than an amorphous ITO film. Also, the higher thedegree of crystallinity of an ITO film, the lower the resistivitythereof tends to be.

To obtain a sufficiently high display brightness in a transmission typedisplay device, the crystalline conductive films preferably exhibit atransmittance of about 70% or more with respect to a light ray having awavelength of about 400 nm and a transmittance of about 80% or more withrespect to a light ray having a wavelength of about 550 nm when thethickness of the crystalline conductive films is 120 nm.

The liquid crystal display device 100 of the preferred embodimentdescribed above is a transmission type display device that usescrystalline ITO films (i.e., transparent conductive films) as theelectrodes 2 and 6 thereof. However, the present invention is alsoapplicable for use in a reflection type liquid crystal display device orin a transflective (i.e., transmission/reflection) type liquid crystaldisplay device. In those alternative liquid crystal display devices, thecrystalline conductive films are preferably made of an Al film or an Alalloy film. This is because Al normally defines a face centered cubiclattice crystal structure and an Al film can function as an alignmentfilm basically in the same way as the ITO film described above.

Alignment Treatment by Energy Beam

As described above, the crystalline conductive films in which thecrystal grains are oriented in a particular orientation directionpreferentially can function as alignment films just as intended withoutbeing subjected to any rubbing treatment. However, the anchoring forceof the crystalline conductive films can be further increased bysubjecting the crystalline conductive films to an alignment treatment aswill be described below.

To increase their anchoring force, the crystalline conductive films maybe subjected to such an alignment treatment by being directly exposed toan energy beam. Examples of such energy beams for use in this preferredembodiment of the present invention include an excimer laser beam, anultraviolet ray, an electron beam, and a particle beam consisting ofions, atoms, molecules or clusters thereof, one of which may be used byitself or some of which may be combined together.

For example, when an excimer laser beam is used as an energy beam, thesurface of the crystalline conductive films can be etchedanisotropically by utilizing the annealing phenomenon or the physicalablation (i.e., substance removing) action of the laser beam. Also, whenthe crystalline conductive films are exposed to an ultraviolet ray,bonding sites, having smaller bonding energy than the energy of theultraviolet ray, are selectively excited, cleaved and collapsed, thusproducing an anisotropic etching action, too. Furthermore, when exposedto an electron beam, the surface of the crystalline conductive films issubject to physical actions (e.g., melted and vaporized) due to thethermal action of the electron beam, thus also achieving anisotropicetching. Furthermore, when exposed to an ion beam, the crystallineconductive films are subject to a sputtering action caused by thecollision of ions onto the surface of the crystalline conductive films,thus also achieving anisotropic etching. By controlling the operation ofirradiation of any of these energy beams onto a target area on thesurface of the crystalline conductive films, a groove structure can bedefined on that surface area. This alignment treatment using such anenergy beam is naturally a non-contact treatment on the crystallineconductive films.

It should be noted that if the crystalline conductive films are exposedto an electrically charged energy beam (e.g., an ion beam, inparticular), then the charges on the crystalline conductive films arepreferably neutralized or removed while the films are being exposed tothe energy beam or just after the films have been exposed to the energybeam. If the crystalline conductive films are exposed to a positivelycharged ion beam, then electrons are preferably supplied onto thesurface of the crystalline conductive films to neutralize positivecharges on the films during the ion beam irradiation.

The effects of increasing the anchoring force of the crystallineconductive films by exposing the films to an energy beam are notnecessarily shape effects (or grating effects) to be achieved bydefining grooves by the anisotropic etching process described above.Alternatively, by exposing the crystalline conductive films to an energybeam, bonds may also be selectively cut off or newly produced around thesurface of the crystalline conductive films, and anisotropy may beproduced for the bonds existing around the surface of the crystallineconductive films. Then, the liquid crystal molecules can also be alignedin a particular orientation direction by utilizing such anisotropicbonding. To create such anisotropic bonding, the crystalline conductivefilms are preferably exposed to a particle beam as disclosed in JapaneseLaid-Open Publications Nos. 11-271773 and 11-271774, for example.

To increase the anchoring force of the crystalline conductive films bydirectly exposing the crystalline conductive films to an energy beam asdescribed above, the crystalline conductive film are preferablyirradiated with the energy beam coming from a direction that defines apredetermined tilt angle with respect to a normal to the surface of thecrystalline conductive film (which is typically parallel to the surfaceof the substrate).

Particularly when the anchoring force of the crystalline conductivefilms is increased by utilizing the shape effects to be achieved when afine groove structure is defined on the surface of the crystallineconductive films by the exposure to the energy beam, a huge number offine grooves, extending in parallel to the preferential orientationdirection of the crystalline conductive films, are preferably defined.To form such grooves, the energy beam preferably comes from a directionthat is defined by a plane including a normal to the surface of thecrystalline conductive films and the preferential orientation directionand that defines a predetermined tilt angle with respect to the normal.When the energy beam comes from such a direction (such an irradiationwill be sometimes referred to herein as “oblique irradiation parallel tothe preferential orientation direction”), bonding components, which areoriented substantially perpendicularly to the direction in which theenergy beam travels, are broken and collapsed preferentially (orselectively). As a result, a groove structure, extending parallel to thepreferential orientation direction of the crystal grains, can be formedefficiently.

When the energy beam is incident obliquely in a preferred embodiment ofthe present invention, a preferred energy beam irradiation direction,which should be associated with the orientation direction of the crystalgrains, is substantially perpendicular to the crystallographic planesthat define the preferential orientation direction.

For example, if the crystalline conductive films have a crystalstructure including crystal grains that are oriented in <111> directionspreferentially, then the crystalline conductive films are preferablyirradiated with the energy beam so as to define an angle of incidence ofabout 30 degrees to about 50 degrees with respect to the normal to thesurface of the crystalline conductive films. On the other hand, if thecrystalline conductive films have a crystal structure including crystalgrains that are oriented in <110> directions preferentially, then thecrystalline conductive films are preferably irradiated with the energybeam so as to define an angle of incidence of about 35 degrees to about55 degrees with respect to the normal to the surface of the crystallineconductive films. When the crystal grains are oriented in the <111>directions preferentially, the crystalline conductive films are morepreferably irradiated with the energy beam so as to define an angle ofincidence of about 30 degrees to about 40 degrees. On the other hand,when the crystal grains are oriented in the <110> directionspreferentially, the crystalline conductive films are more preferablyirradiated with the energy beam so as to define an angle of incidence ofabout 40 degrees to about 50 degrees. In this case, if the angle ofincidence of the energy beam falls outside of these preferred ranges,then the bonding components, which are oriented substantiallyperpendicularly to the direction in which the energy beam travels, aremuch more likely to be cut off. Thus, bonding components that areoriented parallel to the preferential orientation direction of thecrystal grains are broken in great numbers. As a result, the effects ofincreasing the anchoring force diminish.

FIG. 5 schematically illustrates an exemplary configuration for an ionbeam emitter for use in the alignment treatment of the crystallineconductive films in this preferred embodiment.

As shown in FIG. 5, the ion beam emitter preferably includes an ion beamsource 10 from which an ion beam 11 is emitted and an electron source 12from which electrons are emitted to neutralize the electric charges thathave been created by the ion beam 11. In a vacuum chamber 15, which isevacuated by a vacuum pump 14 to create and maintain a reduced pressureatmosphere therein, a stage 16 is preferably provided so as to freelyrotate around a shaft 17. The substrate 1 including the crystallineconductive film (i.e., electrode) 2 (see FIG. 1) thereon is mounted onthe stage 16 and the angle θ of incidence of the ion beam 11 is adjustedwith respect to the crystalline conductive film 2. To neutralizeelectric charges, which are produced on the surface of the crystallineconductive film 2 being exposed to the ion beam 11, the crystallineconductive film 2 is exposed to an electron shower 13 while the film 2is being exposed to the ion beam 11 or just after the film 2 has beenexposed to the ion beam 11. Optionally, the crystalline conductive film2 may be exposed to the ion beam 11 and the electron shower 13simultaneously or alternately a number of times.

The crystalline conductive film 2 is made of an inorganic material asdescribed above. Accordingly, compared to using an organic material, theinner walls of the chamber 15 and the surface of the crystallineconductive film 2 are much less likely to be contaminated. Also, thesurface of the substrate 1 is mostly covered with the crystallineconductive film 2 and no electrons will remain there locally. Thus, noactive components such as TFTs will cause dielectric breakdown due tostatic electricity.

An ion beam emitter is illustrated as an exemplary energy beam emitterin FIG. 5. Alternatively, as disclosed in Japanese Laid-Open PublicationNo. 9-218409, an apparatus for irradiation of an ion beam and anultraviolet ray may also be used. Also, any other energy beam emittermay be formed by a known technique (e.g., by changing the beam sources).

Analysis of Crystalline Conductive Film

The crystalline conductive films formed as described above may beanalyzed in the following manner, for example. Hereinafter, an analysismethod that will be used in specific examples of preferred embodimentsof the present invention and comparative examples will be described.

(1) Analysis of Crystallinity and Crystal Orientation Direction

A thin film XRD analyzer RINTI 500 (produced by Rigaku InternationalCorporation) was used to measure the diffraction intensities under theconditions including a Cu tube (CuK α1 line), a tube current of about200 mA, a tube voltage of about 50 kV, a broad-angle goniometer, asampling angle of about 0.05 degrees, a scanning rate of about 3.0degrees per minute, a scanning axis of 2θ, a fixed angle of about 1.0degree and a rotational velocity of about 120 rpm. The degree ofcrystallinity and crystallinity were evaluated based on the shapes ofrespective diffraction peaks and the integrated intensities.

As for the crystalline ITO film, for example, a diffraction peakrepresenting the (222) plane could be detected when 2θ≈30.5 degrees, adiffraction peak representing the (400) plane could be detected when2θ≈35.4 degrees, and a diffraction peak representing the (440) planecould be detected when 2θ≈51.0 degrees as shown in FIG. 4. Thus, theorientation directions of the crystal grains were defined based on theratio of these peak intensities.

(2) Analysis of Crystal Grain Sizes

The two-dimensional distances of the crystal grains were analyzed byobserving the surface of the crystalline conductive film directly (i.e.,without depositing Au thereon) and perpendicularly to the surface of thefilm using a field emission secondary electron microscope S-900(produced by Hitachi, Ltd). The magnification of the microscope was setto 10⁵, for example.

(3) Surface Observation After Alignment Treatment

The surface shapes of the crystalline conductive film before and afterthe anisotropic etching process were observed by using an atomic forcemicroscope SPI 3700 (produced by Seiko Instruments Inc.) in a resonancemode at a scanning frequency of about 1 Hz. The area under measurementwas about 1 μm square.

(4) Measurement of Spectral Transmittance

The spectral transmittance of the crystalline conductive film wasmeasured in a transmission mode with a spectrophotometer U-4100(produced by Hitachi, Ltd.) by reference to the spectral transmittancein the air. The transmittance of the crystalline conductive film wasmeasured with the thickness thereof converted. Specifically, with thethickness of the crystalline conductive film is 120 nm, thetransmittances thereof with respect to incoming light rays havingwavelengths of about 400 nm and about 550 nm were measured.

Liquid Crystal Display Device

A liquid crystal display device according to a preferred embodiment ofthe present invention includes an inorganic alignment film made of thecrystalline conductive film described above. Thus, the liquid crystaldisplay device needs no rubbing treatment to make the alignment film andensures excellent heat resistance, light resistance and moistureresistance. For that reason, the present invention is particularlyeffectively applicable for use in a projection type liquid crystaldisplay device in which the LCD panel is exposed to intense light andoften has an elevated temperature.

FIG. 6 schematically illustrates an exemplary arrangement for aprojection type liquid crystal display device (which will be referred toherein as a “projector” simply) according to a preferred embodiment ofthe present invention.

As shown in FIG. 6, the projector 200 preferably includes anillumination optical system 210 including a lamp light source 212, acolor separation optical system 230, a relay optical system 220, threeliquid crystal panels (light bulbs) 100R, 100G and 100B, a crosseddichroic prism 242 and a projection lens 252. The liquid crystal lightbulbs 100R, 100G and 100B are arranged in the optical paths of threelight rays representing the three primary colors of red, green and blue(which will be referred to herein as an “R light ray”, a “G light ray”and a “B light ray”), respectively. The light, which has been emittedfrom the illumination optical system 210, is separated by the colorseparation optical system 230 into the R, G and B light rays. Then, theR, G and B light rays are incident onto their associated liquid crystallight bulbs 100R, 100G and 100B. Thereafter, those light rays, modulatedby their associated light bulbs in accordance with the imageinformation, leave the light bulbs so as to be synthesized together atthe crossed dichroic prism 242. The synthesized light is then projectedby the projection lens 252 onto a screen 500 to present an image in fullcolors there.

In the preferred embodiment illustrated in FIG. 6, the color separationoptical system 230 separates the white light into the red (R), green (G)and blue (B) light rays. Alternatively, a color separation opticalsystem for separating the white light into cyan, magenta and yellowlight rays may also be used. As another alternative, a color separationoptical system for separating the white light, emitted from theillumination optical system 210, into four or more light rays inmutually different colors may also be used.

The projector 200 of the preferred embodiment shown in FIG. 6 is athree-panel type that uses the three liquid crystal light bulbs 100R,100G and 100B, the crossed dichroic prism 242 and dichroic mirrors 232and reflective mirrors 206. Alternatively, the R, G and B light rays mayalso be synthesized together by using dichroic mirrors instead of thecrossed dichroic prism 242.

It should be noted that the present invention is applicable for use innot just the three-panel projection type liquid crystal display devicedescribed above but also in a single panel projection type liquidcrystal display device as well. For example, the present invention isalso applicable for use in a device including a single color LCD panelin which micro-color filters for the three primary colors of red, greenand blue are provided for respective pixels. As another alternative, asingle monochrome LCD panel and an optical system for making light raysin the three primary colors incident onto respective pixels of the LCDpanel (consisting of dichroic mirrors and a microlens array, forexample) may also be used in combination.

Also, none of the arrangements described above has to be a frontprojection type device that projects an image from the projectordisposed in front of the screen as shown in FIG. 6. Alternatively, anyof those arrangements is also applicable for use in a rear projectiontype device that projects an image from behind the screen usingreflective mirrors, for example.

On the LCD panels for use in this preferred embodiment, information iswritten by an active-matrix-addressing technique, for example. However,the present invention is not limited to this particular type of liquidcrystal display device but may also be applicable for use in a liquidcrystal display device of simple-matrix-addressing type, an opticaladdressing type or a thermal addressing type (using a laser beam).

Hereinafter, specific examples of preferred embodiments of the presentinvention and comparative examples will be described. It should be notedthat the present invention is in no way limited to the followingillustrative examples.

EXAMPLES NOS. 1 THROUGH 4 AND COMPARATIVE EXAMPLES NOS. 1 THROUGH 4

Crystalline ITO films to be display electrodes (i.e., pixel electrodesand counter electrode) were deposited on transparent glass substrates bythe HDPE process described above. The HDPE process was carried out suchthat plasma created near the transparent glass substrates had a densityof about 10¹³ ions/cm³ to about 10¹⁴ ions/cm³ and a potential of about+10 V to about +30 V. A sintered body of ITO including about 7.5 mass %of SnO₂ was used as a target. The atmosphere had a pressure of about4×10⁻² Pa to about 6.7×10⁻² Pa.

In first and second specific examples of preferred embodiments of thepresent invention, the films were deposited and crystallized at asubstrate temperature Ts of about 200° C. When necessary, the filmsdeposited were annealed at a temperature of about 150° C. to about 300°C.

The results of the thin film XRD pattern analysis and scanning electronmicroscopy (SEM) described above revealed that the crystalline ITO filmsof the first and second specific examples had a degree of crystallinityof at least about 95%, an Ip value (≡I(400)/I(222)) of about 0.1 andcrystal grains that were oriented in <111> directions preferentially.

In a third specific example of a preferred embodiment of the presentinvention, crystalline ITO films were formed by adjusting the depositionconditions and raising the substrate temperature Ts to about 250° C. Asa result, crystalline ITO films, having a degree of crystallinity ofabout 90% and crystal grains that were oriented in <110> directionspreferentially, were obtained.

In a fourth specific example of a preferred embodiment of the presentinvention, crystalline ITO films were deposited at a substratetemperature Ts of about 150° C. As a result, crystalline ITO films,having a degree of crystallinity of about 62%, an Ip value of about0.24, and crystal grains that were oriented in <111> directionspreferentially, were obtained.

On the other hand, in a first comparative example, non-crystalline ITOfilms were deposited by a conventional EB evaporation process. In asecond comparative example, crystalline ITO films were deposited by theHDPE process at a substrate temperature Ts of about 140° C As a result,crystalline ITO films, having a degree of crystallinity of about 57%, anIp value of about 0.35 and crystal grains that were oriented in <100>directions preferentially, were obtained. In a third comparativeexample, crystalline ITO films were deposited by a sputtering process ata substrate temperature Ts of about 200° C. As a result, crystalline ITOfilms, having a degree of crystallinity of about 68%, an Ip value ofabout 0.25 and crystal grains that were oriented in <111> directionspreferentially, were obtained. In a fourth comparative example,crystalline ITO films were formed as in the first specific exampledescribed above and then known alignment films of polyimide weredeposited by a printing process.

Each of these crystalline ITO films was patterned into a predeterminedshape to form a display electrode.

In the first, third and fourth specific examples of preferredembodiments of the present invention and the first through fourthcomparative examples, the crystalline ITO films and polyimide films onthe substrates were exposed to an Ar ion beam by using the ion beamemitter shown in FIG. 5. The angle θ of incidence of the ion beam wasalso associated with the pretilt angle of liquid crystal molecules, forexample. In the crystal structure in which crystal grains were orientedin the <111> directions preferentially, the ion beam was incident on thesubstrates so as to define an angle θ of incidence of about 35 degreesto about 37 degrees with respect to a normal to the surface of thesubstrates. On the other hand, in the crystal structure in which crystalgrains were oriented in the <110> directions preferentially, the ionbeam was incident on the substrates so as to define an angle θ ofincidence of about 45 degrees. The Ar ion beam was directly incident onthe surface of the films on the substrates by accelerating an ionized Argas, which had been generated from an ion source, with an appliedelectric field of about 400 V within a vacuum. In this manner, the filmswere subjected to the alignment treatment.

Thereafter, the upper and lower substrates were bonded together withcell spacers (with a diameter of about 4 μm) and a seal member. In thiscase, the upper and lower substrates were arranged with respect to eachother such that the direction in which treated portions of the filmfaced on one of two substrates was approximately perpendicular to thedirection in which treated portions of the film faced on the othersubstrate. Subsequently, a predetermined liquid crystal material wasinjected into the gap between the substrates within a vacuum, and thenthe injection holes were sealed airtight, thereby obtaining TN-modetransmission type LCD panels.

The electrooptical characteristics of the LCD panels obtained in thismanner were evaluated. Specifically, their transmittances to opticallyrotating light were measured with a polarizing microscope and thecontrast ratios (CR) resulting from an applied voltage of about 5 V werealso measured. In addition, the heat and light resistances thereof werefurther evaluated by a reliability/aging test using a UHP lamp at atemperature of about 80° C. and an illuminance of about 20,000,000 1x.The results are shown in the following Tables 1 and 2. TABLE 1 CrystalTransmittance Alignment Degree of Orientation (%, 120 nm) Ion FilmsCrystallization Ip value 400 nm 550 nm Beam Ex. 1 Crystalline 95% <111>82 95 Obliquely ITO Ip = 0.1 irradiated Ex. 2 Crystalline 95% <111> 8295 Not ITO Ip = 0.1 Irradiated Ex. 3 Crystalline 90% <110> 71 82Obliquely ITO Ip = — Irradiated Ex. 4 Crystalline 62% <111> 73 84Obliquely ITO Ip = 0.24 Irradiated Cmp. 1 Amorphous  5% — 74 83Obliquely ITO (amorphous) Irradiated Cmp. 2 Crystalline 57% <100> 68 78Obliquely ITO Ip = 0.35 Irradiated Cmp. 3 Crystalline 67% <111> 72 82Obliquely ITO Ip = 0.25 Irradiated Cmp. 4 Polyimide — — 61 73 Obliquely(organic) Irradiated

TABLE 2 Liquid Electrooptical crystal Characteristics Orientation CRReliability/aging Uniformity Transmittance (5 V) After 1,000 hours Ex. 1Good 81% 325 No variations in display performance Ex. 2 Good 82% 315 CRdropped by 10% Ex. 3 Good 76% 298 No variations in display performanceEx. 4 Good 75% 297 No variations in display performance Cmp. 1 Fair 70%256 CR dropped by 45% (with tilt (with tilt variation variations)increased) Cmp. 2 Good 73% 271 CR dropped by 15% (with tilt variationsensed) Cmp. 3 Good 72% 276 CR dropped by 5% (with tilt variationproduced) Cmp. 4 Good 62% 242 Air voids created Poor reliability

It was confirmed that in the second specific example in which thecrystalline ITO films had a high degree of crystallinity and the crystalgrains were almost oriented in the same orientation directions, theorientation directions of liquid crystal molecules were alsosufficiently uniform. Also, as can be seen easily by comparing theresults of the first and second specific examples with each other, thereliability increased when the crystalline conductive films wereobliquely exposed to the ion beam. When the surface of the substrates(or more exactly the surface of the crystalline conductive films) thathad been exposed to the ion beam was observed with an atomic forcemicroscope (AFM) or a scanning electron microscope (SEM), it wasconfirmed that a fine groove structure having a regular pattern wasdefined in the preferential orientation directions of the crystal grainsas result of the exposure to the ion beam. Thus, it is believed that theorientation directions of liquid crystal molecules were made furtheruniform due to the beneficial effects achieved by a combination of sucha physical structure and the preferential orientation directions of thecrystal grains.

As already described for the respective examples, it was also confirmedthat when the crystalline conductive films were subjected to thealignment treatment by irradiating the films with an ion beam from adirection that was associated with the preferential orientationdirections of the crystal grains thereof, the liquid crystal moleculescould be anisotropically oriented rather constantly. It was furtherconfirmed that compared to the fourth comparative example in which theconventional alignment films of polyimide were used, the transmittanceof the LCD panel could be increased significantly and far better resultswere obtained in the reliability/aging tests (such as seeing if an imagepersistence phenomenon occurred after a fixed pattern had beendisplayed).

EXAMPLE NO. 5 AND COMPARATIVE EXAMPLE NO. 5

In a fifth specific example of a preferred embodiment of the presentinvention and in a fifth comparative example, a projection type liquidcrystal display device 200 such as that shown in FIG. 6 was fabricatedand the projection performance and aging characteristic thereof wereevaluated. In these examples, TFT LCD panels were used as the liquidcrystal light bulbs. In the fifth specific example, the displayelectrodes of the LCD panel were formed as in the first specific exampledescribed above. In the fifth comparative example on the other hand, theLCD panel included alignment films of polyimide as in the fourthcomparative example described above. The crystalline conductive filmsand polyimide alignment films were exposed to an ion beam at an angle ofincidence of about 37 degrees with respect to a normal to the surface ofthe substrates. TN-mode TFT LCD panels were completed through similarprocess steps to those of the first specific example and the fourthcomparative example described above.

Neither the LCD panel of the fifth specific example nor the LCD panel ofthe fifth comparative example caused any serious problem in theorientation state of liquid crystal molecules. An image persistencephenomenon occurred only in the LCD panel of the fifth comparativeexample, including the alignment films of polyimide, after a fixedpattern had been displayed there for approximately 30 minutes.

The LCD panels of the fifth specific example and the fifth comparativeexample were subjected to a projection aging test, which was carried outat a panel temperature of about 60° C and at 1,500 ANSI lumen. As aresult, the LCD panel of the fifth specific example showed nosignificant variations in contrast ratio or in brightness even after1,000 hours. On the other hand, the LCD panel of the fifth comparativeexample had its contrast ratio decreased from its initial value by about30% and its brightness also decreased by about 25% once the aging timeexceeded approximately 500 hours. When the LCD panel of the fifthcomparative example was observed with a polarizing microscope, it wasdiscovered that a variation in the tilt angle of liquid crystalmolecules on a display panel plane, an increase in the area of a reversetilt region and a decrease in the uniformity of orientation directionsof liquid crystal molecules had been brought about by the projectionaging.

The liquid crystal display device according to any of various preferredembodiments of the present invention described above includes a pixelelectrode and a counter electrode that face each other with a liquidcrystal layer interposed between them. However, the present invention isin no way limited to this particular type of liquid crystal displaydevice but is broadly applicable for use in any of various other typesof liquid crystal display devices. For example, even in an IPS modeliquid crystal display device in which the two electrodes are providedon the surface of one of the two substrates facing a liquid crystallayer, the inorganic alignment film, as well as the electrodes or lines,can be formed by the same manufacturing process step. Thus, themanufacturing process can also be simplified significantly.

In the specific examples of preferred embodiments of the presentinvention described above, the crystalline ITO films were used. However,even if the present invention is applied to crystalline Al or Al alloyfilms, including cubic crystal grains, in substantially the same way,similar effects are also achieved. Also, any other inorganic materialmay be used as well.

In a liquid crystal display device according to any of various preferredembodiments of the present invention described above, the alignmentfilms thereof are crystalline conductive films made of an inorganicmaterial, and need no rubbing treatment. Thus, a highly reliable liquidcrystal display device can be provided by a simplified manufacturingprocess.

According to various preferred embodiments of the present inventiondescribed above, the unwanted dust deposition and uneven treatment,which are often observed in a conventional rubbing treatment, can beeliminated. Thus, various effects including:

-   -   (1) removal of pixel defects such as point defects;    -   (2) elimination of display unevenness from overall pixels and        significant reduction in the variation of operating performance        between individual products;    -   (3) excellent display quality including a high contrast ratio, a        high brightness, and even moving picture display capabilities;        and    -   (4) high productivity and constant supply of quality products at        a reduced cost        are achieved by the present invention. The present invention is        particularly effectively applicable for use in a high-definition        liquid crystal display device that should exhibit rather high        display quality (e.g., a projection type liquid crystal display        device among other things).

While the present invention has been described with respect to preferredembodiments thereof, it will be apparent to those skilled in the artthat the disclosed invention may be modified in numerous ways and mayassume many embodiments other than those specifically described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention that fall within the true spirit andscope of the invention.

1. A method for fabricating a liquid crystal display device, the deviceincluding: a liquid crystal layer; a pair of electrodes for use to applya voltage to the liquid crystal layer; and at least one inorganicalignment film, which makes direct contact with the liquid crystal layerand which is made of a crystalline conductive film, the methodcomprising the steps of: forming the crystalline conductive film, inwhich crystal grains are oriented in a predetermined directionpreferentially, on a substrate; and forming the liquid crystal layer onthe crystalline conductive film.
 2. The method of claim 1, furthercomprising the step of irradiating the crystalline conductive film withan energy beam at an angle that is associated with the predetermineddirection.
 3. The method of claim 2, wherein the step of forming thecrystalline conductive film includes the step of forming the crystallineconductive film in which the crystal grains have a cubic crystallinestructure and are oriented in <111> directions thereof, and wherein thestep of irradiating the crystalline conductive film with the energy beamincludes the step of irradiating the crystalline conductive film suchthat the energy beam defines an angle of incidence of about 30 degreesto about 50 degrees with respect to a normal to the surface of thesubstrate.
 4. The method of claim 2, wherein the step of forming thecrystalline conductive film includes the step of forming the crystallineconductive film in which the crystal grains have a cubic crystallinestructure and are oriented in <110> directions thereof, and wherein thestep of irradiating the crystalline conductive film with the energy beamincludes the step of irradiating the crystalline conductive film suchthat the energy beam defines an angle of incidence of about 35 degreesto about 55 degrees with respect to a normal to the surface of thesubstrate.
 5. The method of claim 2, wherein the step of irradiating thecrystalline conductive film with the energy beam includes the step ofirradiating the crystalline conductive film with at least one energybeam that is selected from the group consisting of an excimer laserbeam, an ultraviolet ray, an electron beam and a particle beam.